The present invention relates to a color filter structure and its manufacturing method. More particularly, the present invention relates to a method for manufacturing the color filter by using the backside exposure method in a self-alignment manner.
Liquid crystal display (LCD) has the advantages of thin thickness, light weight, low radiation and low power consumption, and has become a newly developed computer peripheral industry, and the most important element thereof is a color filter (CF).
Color filter is generally used in the application of the LCD for the display in colors. As shown in FIG. 1, a typical structure of a color filter comprises, from the bottom to the top, a substrate 10, a black matrix 12, color filter elements 14, 16 and 18, and a transparent conductive layer 20, wherein the substrate 10 is made of transparent glass and the color filter elements 14, 16 and 18 are generally composed of the three primary colors of red (R), green (G), and blue (B).
A conventional process for manufacturing a color filter comprises the steps of: providing a substrate 10 made of a material such as glass; depositing the light-blocking material, for example, chromium (Cr), on the substrate 10 by a metal sputtering method; exposing and developing the light-blocking material to form a black matrix (BM) layer 12 in a required pattern by using a photolithographic method; depositing the required color filter elements of red 14, green 16, or blue 18 on the BM 12 by, for example, spinning and photolithography; and forming a transparent conductive layer 20, for example, an indium tin oxide film (ITO film), to complete the fabrication of a color filter structure.
The conventional process needs to repeat the photolithographic process a plurality of times to complete the manufacture of a color filter. Besides, the conventional process is more complicated due to the alignment errors between the structure of the lower part of BM 12 and each individual color filter element where there are overlapping bulges or gaps between the color filter elements. According to the structure as shown in FIG. 1, the green color filter element 16 is shifted to the right and the blue color filter element 18 to the left, thus resulting in a bulged region and a wider division because of the overlap coating between two color filter elements. The flatness of the LCD is thereby affected, which causes the poor arrangement of liquid crystal in these regions.
Furthermore, for a conventional process, in order to form the color filter elements in better alignments, the width of each BM element needs to be increased to cover the area between two adjacent color filter elements and to thereby prevent light leakage. However, the open ratio is limited due to the increase of the width of BM elements, and the brightness of the LCD is thus decreased.
According to the above description of the background of art, conventional color filters have the disadvantages of misalignment in the manufacturing process and uneven structure, which directly affect the arrangement of liquid crystal and the brightness of the LCD. The present invention uses the backside exposure to fabricate a color filter, which can reduce the number of times for using the photomask and also improve the flatness of the color filter. Therefore, one object of the present invention is to form the self-aligned color filter elements with good flatness by combining the methods of etching and backside exposure.
Furthermore, by narrowing the shading area of black matrix between two adjacent color filter elements, the area of color filter elements is increased to enhance the transmittance of backlight and thereby the quality of the LCD is improved. Hence, another object of the present invention is to change the position of the black matrix to be on a transparent conductive layer. In other words, a transparent conductive layer is inserted between the layer of black matrix and the layer of color filer elements. By means of narrowing the width of BM element, increasing the open ratio, and reducing the alignment errors in applying a process window for forming BMs, the brightness of the LCD is enhanced.
According to the aforementioned objects, the present invention provides a method for forming color filter elements in a self-alignment manner without the disadvantages of a conventional process and the defects of a conventional structure. Further, the present invention provides a method of forming the black matrix upon a transparent conductive layer with a view to decreasing the width of BM elements, increasing the open ratio and reducing the errors in applying a process window. Consequently, the brightness of the LCD is enhanced.
To achieve the aforementioned objects, the present invention provides a method for manufacturing a color filter comprising: providing a substrate; forming a first resin layer on the substrate; defining the first resin layer to expose first portions of the substrate; forming a second resin layer on the first portions of the substrate; performing a first back-exposure process to transform the second resin layer into a second layer of color filter elements; defining the first resin layer to expose second portions of the substrate, wherein the remaining first resin layer on the substrate becomes a first layer of color filter elements; forming a third resin layer on the second portions of the substrate; and performing a second back-exposure process to transform the third resin layer into a third layer of color filter elements.
To achieve the aforementioned objects, the present invention provides a color filter structure, which comprises, from the bottom to the top: a substrate, a plurality of self-aligned color filter elements, a transparent conductive layer, and a layer of black matrix, wherein the substrate is made of transparent glass and the color filter elements are composed of the three primary colors of red (R), green (G), and blue (B). The color filter structure of the present invention is featured in that the color filter elements thereof have good flatness, and the BM layer is on the top of the transparent conductive layer, i.e., the transparent conductive layer is located between the BM layer and the layer of color filter elements.
According to the color filter structure and its manufacturing method of the present invention, there are several advantages described as follows: forming the color filter elements in a self-alignment manner by using the backside exposure, and thereby preventing the color filter elements from overlapping; repositioning each BM element to be on each color filter element for avoiding the bulging problem of color resin and thereby obtaining the color filter elements and the transparent conductive layer with good flatness; and further, reducing the width of BM elements by leaving the alignment concern aside, and thereby increasing the open ratio of color filter elements and avoiding the alignment problem in applying a process window.